Medication infusion devices may be used to deliver an infusion media to a subject. Such devices may be implanted to deliver dosages of the infusion media to a selected location in the subject's body, for example, in the vessels, spinal column and/or peritoneal cavity. For example, medication pump devices can include a drive mechanism that includes a reciprocating actuator having a piston and an armature. In some cases, the pump device has a solenoid coil that can be alternately energized and de-energized to reciprocate the piston within a piston chamber between a forward stroke to deliver infusion media to the subject and a return stroke to refill the piston chamber with infusion media.
Pump orientation and/or gravity effects on a pump device can alter the clearances between the piston and piston chamber, affecting the delivery rate of the infusion media. Over time, reciprocal motion of the actuator can result in wear of pump components, which can effect pump performance. Pump orientation and/or gravity effects may also contribute to wear. This disclosure describes an improvement over these prior art technologies.